Preparation of degradable polymeric material

ABSTRACT

There is disclosed the preparation of a degradable polymeric material by applying a degradation-sensitizing reagent to the surface of a polymeric material and then diffusing the reagent into such surface.

United States Patent Taylor et al.

[ 5] Mar. 19, 1974 PREPARATION OF DEGRADABLE POLYMERIC MATERIAL [75]Inventors:

Assignee:

Filed:

Appl. No.2

Lynn J. Taylor, Haslett; John W. Tobias, E. Lansing, both of Mich.

Owens-Illinois, Inc., Toledo, Ohio Dec. 8, 1971 US. Cl. 220/1 R, 117/94,117/l38.8 E, 177/160 R, 117/161 R, 220/DIG. 30, 260/23 Int. Cl. B44d1/02 Field of Search 117/94. 161 R, 138.8 E; 260/23 H; ZZO/DIG. 30, 1 R

References Cited UNITED STATES PATENTS Lamb 220/D1G. 30

Moore 220/DIG. 3O

Stager et a1 117/94 Newland et a1.... 260/23 H Bassemir et a1 117/161 RXBassemir et a1 117/161 RX Maekawa 117/160 R Abu-lsa 1 17/160 R PrimaryExaminerEdward G. Whitby Attorney, Agent, or Firm-Donald Keith WeddingABSTRACT 10 Claims, No Drawings PREPARATION OF DEGRADABLEPOLYIVIERICMATERIAL BACKGROUND OF THE INVENTION This invention relates to novelplastic compositions having enhanced environmental degradability.

The advent of plastics has given rise to improved methods of packaginggoods. For example, polyethylene and polypropylene plastic films, bags,bottles, styrofoam cups and blister packages have the advantages ofbeing chemically resistant, relatively unbreakable, light in weight andtranslucent or transparent. The increasing use of plastics in packagingapplications has created a serious waste disposal problem. Burning ofthese plastic materials is unsatisfactory since it adds to air pollutionproblems.

Unlike some other packaging materials, such as paper and cardboard,plastics are not readily destroyed by the elements of nature. Thus,burying them is not an effective means of disposal, and can beexpensive.

Plastics are biologically recent developments, and hence are not easilydegradable by micro-organisms which attack most other forms of organicmatter and return them to the biological life cycle. it has beenestimated that it may take millions of years for organisms to evolvewhich are capable of performing this function. in the meantime, plasticcontainers and packaging films are beginning to litter the countrysideafter being discarded by careless individuals.

One approach to the alleviation of the problem of plastics waste andlitter would involve the development of novel polymeric compositionswhich undergo accelerated degradation under environmental conditions.This general approach has been described in the prior art. For example,reference is made to British Patent Specification 1,128,793, whichdescribes ethylenecarbon monoxide copolymers which undergo rapiddeterioration when subjected to sunlight.

An alternative approach involves the use of oxygen, rather thansunlight, as the primary initiator of polymer degradation.

The enhancement of the rate of environmental deterioration of plasticsthrough the use of oxidationpromoting additives is known in the priorart. For example, the preparation of degradable polyolefin filmscontaining certain organic derivatives of transition metals is describedin US. Pat. No. 3,454,510.

The use of degradation-sensitizing additives, particularly those whichaccelerate degradation by thermal or oxidative processes, can becomplicated as a result of undesired degradation of the polymercomposition during the processing of a molten thermoplastic. Theinvention at bar is intended to avoid this difficult prior art problem.

In accordance with this invention, a polymericmaterial-degradation-sensitizing non-polymeric reagent is applied to thesurface of a polymeric material and diffused into such surface so as toprepare a degradable polymeric material.

As used herein, the term degradation-sensitizing reagent is intended toinclude any inorganic or organic, non polymeric reagent which willpromote or accelerate the degradation of a polymeric material when suchreagent is appropriately diffused into the surface thereof. Theresulting degradation may be by any suitable function or mechanismincluding heat, light, oxygen, moisture, micro-organisms, etc.

Preferred polymer-degradation sensitizing reagents are those whichaccelerate autoxidation and/or photooxidation processes. These includefree-radical initiating reagents, metallo-organic autoxidationcatalysts, readily autoxidized organic compounds, and photosensitizers.

Specific examples of useful polymer-degradation sensitizing reagentsinclude organic peroxides and hydroperoxides, such as tert-butylhydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide,2,5-dimethylhexane-2,S-dihydroperoxide, pmenthane hydroperoxide;l,l,3,3-tetramethylbutyl hydroperoxide, acetyl peroxide, benzoylperoxide, pchlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide,ditoluoyl peroxide, decanoyl peroxide, lauroyl peroxide, isobutyrylperoxide diisononanoyl peroxide, pelargonyl peroxide, tert-butylperoxyacetate, tert-butyl peroxymaleic acid, tert-butylperoxy-isobutyrate, tertbutyl peroxypivalate, tert-butyl peroxybenzoate,tertbutyl peroxycrotonate, tert-butyl peroxy-( 2- ethylhexanote),2,5-dimethyl-2,5-bis-(2- ethylhexanoylperoxy) hexane,2,5-dimethyl-2,5-bis- (benzoylperoxy) hexane,2,5-dimethyl-2,5-bis-(tertbutyl-peroxy) hexane,2,5-dimethyl-2,5-bis-(tertbutylperoxy)-hexyne-3,-di-tert-butyl late, 1,l ,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di-tert-butyl peroxide,di-tert-amyl peroxide, tert-amyltert-butyl peroxide, 1 l-tert-butylperoxy-3 ,3 ,5- trimethyl cyclohexane,bis-(tert-butylperoxy)-diisopropylbenzene,n-butyl-4,4-bis-(tert-butylperoxy) valerate, dicumyl peroxide, acetylacetone peroxide, methyl ethyl ketone peroxide, peroxide, peroxide,tertbutylperoxy isopropyl carbonate, 2,2-bis-(tert-butylperoxy)butane,di-(Z-ethylhexyl) peroxydicarbonate, and bis-(4-tert-butylcyclohexyl)peroxydicarbonate.

Organic azo compounds may also be employed as polymer-degradationsensitizing reagents. Typical examples include2-azo-bis-isobutyronitrile, Z-azo-bispropionitrile,dimethyl-2-azo-bis-isobutyrate, l-azobisl-cyclohexanecarbonitrile,2-azo-bis-2- methylheptanitrile, 2-azo-bis-2-methylbutyronitrile,4-azo-bis-4-cyanopentanoic acid, azodicarbonamide, and azobenzene.

Also useful as polymer-degradation sensitizing reagents aremetallo-organic compounds, particularly those derived from transitionmetals. Specific examples include acetates, acetylacetonates,benzoyl-acetonates, dodecylacetylacetonates, benzoates, butyrates,citrates, cyclohexanebutyrates, disalicylideneethylenediamine chelates,2-ethylhexanoates, laurates, linoleates, linolenates, myristates,naphthenates, neodecanoates, oleates, palmitates, phthalocyanines,stearates, tallates, tartrates, 3,5,5-trimethyl hexanoates, andvalerates, all derived from the following metals: cobalt, chromium,copper, iron, nickel, and manganese. In such materials, the transitionmetal may be present in any readily accessible valence state; forexample, cobalt may be present in the cobaltous or cobaltic state,copper inthe cuprous or cupric state, and iron in the ferrous or ferricstate.

A variety of organic materials which undergo facile autoxidation mayalso be employed as polymerdegradation sensitizing reagents. Typicalexamples include olefinic materials such as l-hexadecene, 1- docosene,allyl benzene, methallyl benzene, l-allyl naphthalene, isobutylenetrimer, isobutylene tetramer, dicyclopentadiene, indene,alpha-phellandrene, and

diperoxyphthag,

squalene; ethers such as polyethylene glycol and its esters,polypropylene glycol and its esters, poly(tetrahydrofuran), dibenzylether, bis-(alphamethylbenzyl)ether, and p-dibenzyloxybenzene; acetalssuch as citral dimethyl acetal, isosafrole, methyl eugenol, safrole,dihydrosafrole, and phenylacetaldehyde diethyl acetal', amines such asbenzylidimethylamine, N,N-dibenzylaniline, 4,4'-methylene bis-(N,N-dimethylaniline 4,4 ,4 '-methylidynetris-( N,N- dimethylaniline),p,p'-benzylidene bis(N,N- dimethylaniline), oleylamine, linoleylamine,and spermine; aldehydes such as decanal, dodecanal, citral, citronellal,cinnamaldehyde, alpha-n-hexylcinnamaldehyde, anisaldehyde,p-isopropylbenzaldehyde, p-benzyloxybenzaldehyde, andp-noctyloxybenzaldehyde; aromatic compounds such as n-dodecyl-benzene,dimethylnaphthalene (various isomers), diphenylmethane, bibenzyl,phenylcyclohexane, tetrahydronaphthalene, fluorene, xanthene, l,3,S-triisopropylbenzene, 1,2-dihydronaphthalene, and9,10-dihydroanthracene; organic boron compounds such astri-n-hexylborane and tri-noctylborane; organic phosphorous compoundssuch as tribenzyl phosphite, trilaurylphosphite, and trilaurylphosphine;natural oils such as castor oil, fish oil, linseed oil, tall oil, soyaoil, tung oil, safflower oil, and oiticica oil; unsaturated fatty acidssuch as oleic acid, linoleic acid, linolenic acid, elaeostearic acid,ricinoleic acid, and erucic acid; esters of unsaturated fatty acids,such as butyl oleate, monoolein, diolein, triolein, polyethylene glycolmono-oleate, polyethylene glycol dioleate, methyl linoleate, and methyllinolenate; thiols such as l-dodecanethiol, p-toluenethiol, benzylmercaptan, 2-mercaptobenzothiazole, and 2- mcrcaptobenzimidazole; andnatural and synthetic resins such as rosin, limed rosin, ester gum,terpene resins, conmarone-idene resins, alkyd resins, unsaturatedpolyesters, polymers and copolymers of butadiene, and polymers andcopolymers of isoprene.

A variety of organic photosensitizers may also be used aspolymer-degradation sensitizing reagents. Typical examples of usefulphotosensitizers include ketones such as acetophenone, acetoin,l'-acetonaphthone, 2'- acetonaphthone, anisoin, anthrone, bianthrone,benzil, benzoin, benzoin methyl ether, benzoin isopropyl ether,l-decalone, 2-decalone, benzophenone, pchlorobenzophenone, dibenzalacetone, benzoylacetone, benzylacetone, deoxybenzoin,2,4-dimethylbenzophenone, 2,5-dimethylbenzophenone,3,4-dimethylbenzophenone, 4-benzoylbiphenyl, butyrophenone,9-fluorenone, 4,4-bis-(dimethylamino)- benzophenone,4-dimethylaminobenzophenone, dibenzyl ketone, 4-methylbenzophenone,propiophenone, benzanthrone, l-tetralone, 2-tetralone, valerophenone,4-nitrobenzophenone, di-n-hexyl ketone, isophorone, and xanthone;quinones such as anthraquinone, laminoanthraquinone,Z-amino-anthraquinone, lchloroanthraquinone, 2-chloroanthraquinone,lmethyl-anthraquinone, 2-methylanthraquinone, lnitroanthraquinone,2-phenylanthraquinone, 1,2- naphthoquinone, 1,4-naphthoquinone,2-methyl-l,4- naphthoquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, and phenanthrenequinone; aromatic hydrocarbons suchas naphthalene, anthracene, and phenanthrene; nitro compounds such asnitrobenzene, p-nitroanisole, 4-nitrobiphenyl, and pnitroaniline;organic sulfur compounds such as diphenyl disulfide, dibenzyl disulfide,dibenzoyl disulfide, tetramethylthiuram monosulfide, tetramethylthiuramdisulfide, and p-toluenesulfinic acid; halogenated organic compounds,such as chlorinated paraffins, chlorinated biphenyls and polyphenyls,chlorinated toluenes, chlorinated xylenes, benzal chloride, benzhydrylchloride, chlorinated naphthalenes, tetrachlorotetrahydronaphthalene,phenacyl chloride, phenacyl bromide, and styrene dibromide; and aromaticamines such as diphenylamine, triphenylamine, andN-phenyl-betanaphthylamine.

Organic dyes may also be employed as polymerdegradation sensitizingreagents. Typical examples include Acridine Orange, Acridine Yellow,Alizarin, Azure B, Brilliant Green, Bromthymol Blue, Chlorazol Black E,Congo Red, Crystal Violet, N,N-Dimethyl-pphenylazo-aniline, Eosin Y,Fluorescein, Indigo, Malachite Green, Martius Yellow, Methylene Blue,Methylene Violet, Methyl Orange, Methyl Red, Orange 11, Pararosaniline,Rhodamine B, Rose Bengal, and So]- vent Violet 9. Use of organic dyes isparticularly attractive in those instances in which it is desired toeffect decoration and sensitize degradation at the same time.

It should be understood that combinations of two or morepolymer-degradation sensitizing reagents may be employed in the practiceof this invention.

Any suitable polymeric material may be treated in accordance with thisinvention including polymers and copolymers. Typical organic polymers(and copolymers) contemplated especially include polyethylene,polypropylene, poly( l-butene), poly(4-methyll pentene),ethylene-propylene copolymers, ethylene-1- butene copolymers,ethylene-l-hexene copolymers, ethylene-vinyl acetate copolymers,ethylene-ethyl acrylate copolymers, ethylene-acrylic acid copolymers andtheir salts, polystyrene, polyvinyl chloride, poly(vinylidene chloride),polyvinyl fluoride, poly(vinylidene fluoride), polyoxymethylene,poly(ethylene oxide), poly(- propylene oxide), polyvinyl alcohol,polyvinyl acetate, polyvinyl formal, polyvinyl butyral, poly(methylacrylate), poly(ethyl acrylate), poly(caprolactam), poly-(hexamethyleneadipamide), poly(ethylene terephthalate), vinylchloride-vinyl acetate copolymers, styrenebutadiene copolymers,styrene-isoprene copolymers, cellulose and cellulosic materials(including paper and paper board), cellulose acetate, cellulosepropionate, cellulose acetate butyrate, ethyl cellulose, methylcellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.Preferred polymers include polyethylene, polypropylene,poly(4-methyl-l-pentene), polystyrene and polyvinylchloride.

The reagent is applied as a continuous or discontinuous coating directlyto the surface of the polymeric material. The coating may be of anysuitable pattern, geometric arrangement, etc., and may also conveyinformation, e.g., labeling, advertisements, etc.

As used herein the term coating is intended to be inclusive of othersimilar terms such as film, deposit, layer, finish, spread, covering,etc.

The actual application of the reagent coating may be by any suitablemeans such as wet or dry spraying, dipping, printing, brushing, rollercoating, electrodeposition, etc.

Preferably the reagent coating is applied in a liquid form or state.Likewise, the reagent coating may contain or be combined with othersuitable materials such as solvent, plasticizers, polymeric binders,surfactants, etc.

The diffusion of the reagent into the polymeric surface may be by anysuitable means or technique.

In one such technique, the reagent coating and/or the polymeric materialare selectively heated to a temperature sufficient to promote diffusionwithout having an undue or substantial deleterious effect on thepolymeric material. Such heat may be applied by any conduction,convection, and/or radiation means such as passage through an oven,flame contact, and electromagnetic radiation such as infra-red, visible,ultraviolet, and microwave radiation.

In another technique, the reagent coating is exposed to an appropriatechemical substance for promotion of the diffusion, such as immersion ina gaseous or liquid compound especially one capable of softening orplasticizing the polymeric material.

Another technique comprises merely allowing the reagent coating andpolymeric material to diffuse with time in a suitable environment.

Not all of the reagent coating ingredients may diffuse into thepolymeric material. Any residue on the polymeric surface may be removedby any appropriate method such as wiping, washing, etc.

The polymeric material may be of any suitable geometric shape orconfiguration and may comprise containers, films, and other plasticbodies.

In comparison to alternative methods of preparing mixtures of organicpolymers and degradationsensitizing reagents, the practice of thisinvention offers the following advantages. As previously noted,degradation during the melting and shaping of thermoplastic materials isavoided. The coating composition containing the degradation-sensitizingreagent(s) can be applied selectively to certain points or areas of aplastic article, in order to control the manner in which the articlewill collapse as a resulting of partial degradation and/r mechanicalcrushing. If desired, the application of the degradation-sensitizingreagent can be combined with a decoration process. If the plasticarticle is a container, application of the degradation-sensitizingreagent to the outer surface will ensure that diffusion will proceedfrom the outer surface inward, thus minimizing the possibility that thedegradation-sensitizing reagent can come into contact with the productsubsequently packaged in the container.

The following examples represent some of the best embodimentscontemplated by the inventors in the practice of this invention.

EXAMPLE 1 A small quantity (ca. 0.5-1. 0g.) of each of the solids listedbelow was placed in a 50-ml. polypropylene beaker. The beakers were thenplaced in an oven and heated 16 hours in air at 120C. In each case, thepolypropylene was stained by the additive, and mechanical embrittlementindicated that the polypropylene had undergone extensive degradation.

Cobalt 2-ethylhexanoate Cobaltic acetylacetonate Cobaltousacetylacetonate Chromic acetylacetonate Ferrous stearate Ferricacetylacetonate Manganic acetylacetonate Manganous acetylacetonateNickel acetylacetonate EXAMPLE 2 A sample (ca. 0.5-1.0 ml.) of each ofthe liquid driers listed below was placed in a 50 ml. polypropylenebeaker. The beakers were heated 24 hours in air at l 10C., then examinedfor staining (indicative of diffusion of the additive into thepolypropylene) and cracking (indicative of mechanical damage due tochemical degradation). In each case, both staining and cracking wereobserved.

Cobalt tallate 6 percent Cobalt linoleate 6 percent Cobalt neodecanoate12 percent Copper neodecanote 6 percent Iron neodecanoate 6 percent Irontallate 6 percent Manganese naphthenate 6 percent Nickel neodecanoate 10percent EXAMPLE 3 A sample of each of the liquids listed below wasplaced in the bottom of a 50 ml. polypropylene beaker, which was stainedby heating one-half hour at 1 10C. Excess liquid was removed from thebeakers, which were then exposed for 136 hours to the light of a 275watt sunlamp. In each case, gentle flexing of the treated beaker led tothe development of cracks, whereas a similarly treated additive-freepolypropylene beaker failed to crack.

Cobalt linoleate Cobalt neodecanoate Copper neodecanoate Iron linoleateIron neodecanoate EXAMPLE 4 A sample (ca. 0.5 g.) of each of the dyesindicated below was placed in the bottom of a 50 ml. polypropylenebeaker. Diffusion of the dye into the polymer was promoted by heating 24hours at C. in a nitrogen atmosphere. After removal of excess additive,the stained beakers were subjected to intense (ca. 20,000microwattslcm?) ultraviolet radiation, in air, for 48 hours. In the caseof the following dyes, this irradiation caused severe damage to thestained portion of the beaker.

Acetosol Red BLS Acridine Orange Acridine Yellow Chlorazol Black E EosinY Phenazo Brilliant Scarlet R.O.

Rhodamine B Base We claim:

1. A process for preparing a degradable polymeric composition by thechemical modification of a polymeric material, which process comprisesapplying a degradation-sensitizing reagent to the surface of a polymericmaterial and then diffusing the reagent into such surface.

2. The process of claim ll wherein the polymeric material is selectedfrom polyethylene, polypropylene, poly(4-methyl-l-pentene), polystyrene,and polyvinylchloride.

3. The process of claim 1 wherein the degradationsensitizing reagent isselected from free-radical initiat- 7. The process of claim 1 whereinthe polymeric material is in the geometric shape of a container.

8. As an article of manufacture, a degradable polymeric substrate havinga degradation-sensitizing reagent diffused into its surface.

9. The invention of claim 8 wherein the substrate is a container.

10. The invention of claim 9 wherein the polymeric material is selectedfrom polyethylene, polypropylene, poly(4-methyl-l-pentene), polystyrene,and polyvinylchloride.

2. The process of claim 1 wherein the polymeric material is selected from polyethylene, polypropylene, poly(4-methyl-1-pentene), polystyrene, and polyvinylchloride.
 3. The process of claim 1 wherein the degradation-sensitizing reagent is selected from free-radical initiating reagents, metallo-organic autoxidation catalysts, readily autoxidized organic compounds, and photosensitizers.
 4. The process of claim 1 wherein the degradation-sensitizing reagent is selected from organic peroxides, organic hydroperoxides, organic azo compounds, metallo-organic compounds, organic materials which undergo facile autoxidation, organic photosensitizers, and organic dyes.
 5. The process of claim 1 wherein the diffusing of the reagent is accomplished by the application of heat.
 6. The process of claim 1 wherein the reagent is applied as a continuous layer to the surface.
 7. The process of claim 1 wherein the polymeric material is in the geometric shape of a container.
 8. As an article of manufacture, a degradable polymeric substrate having a degradation-sensitizing reagent diffused into its surface.
 9. The invention of claim 8 wherein the substrate is a container.
 10. The invention of claim 9 wherein the polymeric material is selected from polyethylene, polypropylene, poly(4-methyl-1-pentene), polystyrene, and polyvinylchloride. 